This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Platelets are small cell fragments that circulate in the bloodstream. They play a key role in controlling bleeding by their ability to form "plugs" at sites of tissue injury. Some patients have high platelet counts that may be associated with bleeding or clotting problems that can predispose to heart attacks or stroke. The genes that control platelet production are largely unknown;their identification would allow more precise diagnostic tests, risk assessment, and potential new targets for therapy. Platelets do not have nuclei;however they do carry a set of different genes from the precursor bone marrow cells from which they originate. These gene transcripts (RNAs) are present at different abundance levels, i.e some of them are present at very high number, whereas others are very difficult to detect. We will try to use sophisticated laboratory methods to identify new platelet genes that may be associated with abnormally high platelet counts. To collect platelets for this study, we will use standard procedures that are routinely used for blood isolation. All blood samples will be obtained by venipuncture, i.e. thawing small volumes (15 to 30 mL [1-2 tablespoons]) of blood from a vein in one's arm. Blood will be used for the source of platelets for gene (RNA) analysis and white blood cells will be used for isolation of DNA. The remaining sample (plasma and red blood cells) will be properly discarded.